Interpretive Summary: In our previous work, we demonstrated that four months of a blueberry-enriched (BB) diet prevented impaired object recognition memory in aged rats. In this study, we determined whether one and two-month BB diets would have a similar effect and whether the benefits would disappear promptly after terminating the diets and whether a one-month BB diet can actually reverse existing object memory impairment in aged rats.
We used Fisher 344 rats were fed an appropriate control diet or one or two months of the BB diet before being tested for memory at 19 months of age. Rats were tested for memory at 19 months and again at 20 months after a month of maintenance on a 2% blueberry-enriched or control diet.
The results showed that the one-month and two-month BB diet groups performed similarly and significantly better than controls. The two-month BB-diet group, but not the one-month group, continued to perform well even after a subsequent month on a standard lab diet. Also the 19-month old rats performed near chance,meaning that their memory performance was no better than if they had been choosing at random (i.e., 50%).
At 20 months of age, the rats who had been fed the BB diet had significantly better memory scores, while the control diet group showed a slight decline. The change in memory scores differed significantly between the two diet groups.
Our findings suggest that a considerable degree of age-related object memory decline in aged rats can be both prevented and reversed by brief time on blueberry-enriched diets.

Technical Abstract:
Objective
Previously, four months of a blueberry-enriched (BB) antioxidant diet prevented impaired object recognition memory in aged rats. Experiment 1 determined whether one and two-month BB diets would have a similar effect and whether the benefits would disappear promptly after terminating the diets. Experiment 2 determined whether a one-month BB diet can subsequently reverse existing object memory impairment in aged rats.
Methods
In Experiment #1, Fischer 344 rats were maintained on an appropriate control diet or on one or two months of the BB diet prior to testing object memory at 19 months post-natal (p.n.). In Experiment #2, rats were tested for object recognition memory at 19 months and again at 20 months after a month of maintenance on a 2% blueberry-enriched or control diet.
Results
In Experiment 1, the control group performed no better than chance, while the one-month and two-month BB diet groups both performed similarly and significantly better than controls. The two-month BB-diet group, but not the one-month group, maintained its performance over a subsequent month on a standard laboratory diet. In Experiment 2, the 19-month old rats performed near chance. At 20 months of age, the rats subsequently maintained on the BB diet significantly increased their object memory scores , while the control diet group exhibited a non-significant decline. The change in object memory scores differed significantly between the two diet groups.
Conclusions
These results suggest that a considerable degree of age-related object memory decline in aged rats can be both prevented and reversed by brief maintenance on blueberry-enriched diets.